• The Chickens

    You must buy 100 chickens for exactly $100, and purchase at least one chicken from each store.

    The first store charges 5 cents/chicken, the second charges $1/chicken and the third charges $5/chicken.

    How many chickens should you buy from each store?

    Spoiler

    80 from store 1 = $4
    1 from store 2 = $1
    19 from store 3 = $95

  • The Criminal

    A man was killed on Sunday morning. His wife found the body and called the police. The police arrived and questioned the chef, maid, butler, and gardener.

    Their alibis were:
    Chef – making breakfast
    Maid – getting mail
    Butler – setting table
    Gardener – watering plants
    The police immediately arrested the criminal.

    Who was it and how did they know?

    Spoiler

    The maid. Mail isn\’t delivered on Sunday

  • The Room With Two Doors

    You\’re in a room with two doors. There\’s a guard at each door. One door is the exit, but behind the other door is something that will kill you. You\’re told that one guard always tells the truth and the other guard always lies. You don\’t know which guard is which. You are allowed to ask one question to either of the guards to determine which door is the exit. What question should you ask?

    Spoiler

    Ask either guard what door the other guard would say is the exit, then choose the opposite door.

    If you ask the guard who always tells the truth, he knows the other guard would lie, so he\’ll point you to the door leading to death. If you ask the guard who always lies, he knows the other guard would truthfully show you the exit, so he\’ll lie and point you to the door leading to death.

    An alternate solution is to ask a guard what they would answer if you were to ask them which door was the exit, then choose that door. The truthful guard will point to the correct exit, but the lying guard will too. Here\’s why. If you asked him what door was the exit, he would normally lie and point to the death door, but you asked him what he would say if you asked what door was the exit, and in order to lie to that question, he will point you to the exit.

  • The Eight Coins

    You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, how can you determine which coin is counterfeit using the scale only twice?

    Spoiler

    First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it\’s the counterfeit. If they\’re equal weight, the third coin is the counterfeit.

  • Glasses of water

    There are six glasses in a row. The first three are full of water, and the next three are empty. By moving only one glass how can you make them alternate between full and empty?

    Spoiler

    Pour the water from the 2nd glass into the 5th glass 😉